2 use std::collections::HashMap;
5 use syntax::codemap::Span;
6 use syntax::visit::FnKind;
7 use utils::{span_lint, span_help_and_lint, snippet, snippet_opt, span_lint_and_then};
9 /// **What it does:** Checks for structure field patterns bound to wildcards.
11 /// **Why is this bad?** Using `..` instead is shorter and leaves the focus on
12 /// the fields that are actually bound.
14 /// **Known problems:** None.
18 /// let { a: _, b: ref b, c: _ } = ..
21 pub UNNEEDED_FIELD_PATTERN,
23 "struct fields bound to a wildcard instead of using `..`"
26 /// **What it does:** Checks for function arguments having the similar names
27 /// differing by an underscore.
29 /// **Why is this bad?** It affects code readability.
31 /// **Known problems:** None.
35 /// fn foo(a: i32, _a: i32) {}
38 pub DUPLICATE_UNDERSCORE_ARGUMENT,
40 "function arguments having names which only differ by an underscore"
43 /// **What it does:** Detects closures called in the same expression where they are defined.
45 /// **Why is this bad?** It is unnecessarily adding to the expression's complexity.
47 /// **Known problems:** None.
54 pub REDUNDANT_CLOSURE_CALL,
56 "throwaway closures called in the expression they are defined"
59 /// **What it does:** Detects expressions of the form `--x`.
61 /// **Why is this bad?** It can mislead C/C++ programmers to think `x` was
64 /// **Known problems:** None.
73 "`--x`, which is a double negation of `x` and not a pre-decrement as in C/C++"
76 /// **What it does:** Warns on hexadecimal literals with mixed-case letter digits.
78 /// **Why is this bad?** It looks confusing.
80 /// **Known problems:** None.
84 /// let y = 0x1a9BAcD;
87 pub MIXED_CASE_HEX_LITERALS,
89 "hex literals whose letter digits are not consistently upper- or lowercased"
92 /// **What it does:** Warns if literal suffixes are not separated by an underscore.
94 /// **Why is this bad?** It is much less readable.
96 /// **Known problems:** None.
100 /// let y = 123832i32;
103 pub UNSEPARATED_LITERAL_SUFFIX,
105 "literals whose suffix is not separated by an underscore"
108 /// **What it does:** Warns if a integral constant literal starts with `0`.
110 /// **Why is this bad?** In some languages (including the infamous C language and most of its
111 /// familly), this marks an octal constant. In Rust however, this is a decimal constant. This could
112 /// be confusing for both the writer and a reader of the constant.
114 /// **Known problems:** None.
122 /// println!("{}", a);
126 /// prints `123`, while in C:
129 /// #include <stdio.h>
133 /// printf("%d\n", a);
137 /// prints `83` (as `89 == 0o123` while `123 == 0o173`).
139 pub ZERO_PREFIXED_LITERAL,
141 "integer literals starting with `0`"
145 #[derive(Copy, Clone)]
146 pub struct MiscEarly;
148 impl LintPass for MiscEarly {
149 fn get_lints(&self) -> LintArray {
150 lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL,
151 DOUBLE_NEG, MIXED_CASE_HEX_LITERALS, UNSEPARATED_LITERAL_SUFFIX,
152 ZERO_PREFIXED_LITERAL)
156 impl EarlyLintPass for MiscEarly {
157 fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
158 if let PatKind::Struct(ref npat, ref pfields, _) = pat.node {
160 let type_name = npat.segments.last().expect("A path must have at least one segment").identifier.name;
162 for field in pfields {
163 if field.node.pat.node == PatKind::Wild {
167 if !pfields.is_empty() && wilds == pfields.len() {
168 span_help_and_lint(cx,
169 UNNEEDED_FIELD_PATTERN,
171 "All the struct fields are matched to a wildcard pattern, consider using `..`.",
172 &format!("Try with `{} {{ .. }}` instead", type_name));
176 let mut normal = vec![];
178 for field in pfields {
179 if field.node.pat.node != PatKind::Wild {
180 if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
185 for field in pfields {
186 if field.node.pat.node == PatKind::Wild {
190 UNNEEDED_FIELD_PATTERN,
192 "You matched a field with a wildcard pattern. Consider using `..` instead");
194 span_help_and_lint(cx,
195 UNNEEDED_FIELD_PATTERN,
197 "You matched a field with a wildcard pattern. Consider using `..` \
199 &format!("Try with `{} {{ {}, .. }}`",
201 normal[..].join(", ")));
209 fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
210 let mut registered_names: HashMap<String, Span> = HashMap::new();
212 for arg in &decl.inputs {
213 if let PatKind::Ident(_, sp_ident, None) = arg.pat.node {
214 let arg_name = sp_ident.node.to_string();
216 if arg_name.starts_with('_') {
217 if let Some(correspondence) = registered_names.get(&arg_name[1..]) {
219 DUPLICATE_UNDERSCORE_ARGUMENT,
221 &format!("`{}` already exists, having another argument having almost the same \
222 name makes code comprehension and documentation more difficult",
223 arg_name[1..].to_owned()));;
226 registered_names.insert(arg_name, arg.pat.span);
232 fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
234 ExprKind::Call(ref paren, _) => {
235 if let ExprKind::Paren(ref closure) = paren.node {
236 if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
237 span_lint_and_then(cx,
238 REDUNDANT_CLOSURE_CALL,
240 "Try not to call a closure in the expression where it is declared.",
242 if decl.inputs.is_empty() {
243 let hint = snippet(cx, block.span, "..").into_owned();
244 db.span_suggestion(expr.span, "Try doing something like: ", hint);
250 ExprKind::Unary(UnOp::Neg, ref inner) => {
251 if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
255 "`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
258 ExprKind::Lit(ref lit) => {
260 let LitKind::Int(value, ..) = lit.node,
261 let Some(src) = snippet_opt(cx, lit.span),
262 let Some(firstch) = src.chars().next(),
263 char::to_digit(firstch, 10).is_some()
266 for ch in src.chars() {
267 if ch == 'i' || ch == 'u' {
269 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
270 "integer type suffix should be separated by an underscore");
276 if src.starts_with("0x") {
277 let mut seen = (false, false);
278 for ch in src.chars() {
280 'a' ... 'f' => seen.0 = true,
281 'A' ... 'F' => seen.1 = true,
282 'i' | 'u' => break, // start of suffix already
286 if seen.0 && seen.1 {
287 span_lint(cx, MIXED_CASE_HEX_LITERALS, lit.span,
288 "inconsistent casing in hexadecimal literal");
290 } else if value != 0 && src.starts_with('0') {
291 span_lint_and_then(cx,
292 ZERO_PREFIXED_LITERAL,
294 "this is a decimal constant",
296 db.span_suggestion(lit.span, "if you mean to use a decimal constant, remove the `0` to remove confusion:", src[1..].to_string());
297 db.span_suggestion(lit.span, "if you mean to use an octal constant, use `0o`:", format!("0o{}", &src[1..]));
302 let LitKind::Float(..) = lit.node,
303 let Some(src) = snippet_opt(cx, lit.span),
304 let Some(firstch) = src.chars().next(),
305 char::to_digit(firstch, 10).is_some()
308 for ch in src.chars() {
311 span_lint(cx, UNSEPARATED_LITERAL_SUFFIX, lit.span,
312 "float type suffix should be separated by an underscore");
324 fn check_block(&mut self, cx: &EarlyContext, block: &Block) {
325 for w in block.stmts.windows(2) {
327 let StmtKind::Local(ref local) = w[0].node,
328 let Option::Some(ref t) = local.init,
329 let ExprKind::Closure(_, _, _, _) = t.node,
330 let PatKind::Ident(_, sp_ident, _) = local.pat.node,
331 let StmtKind::Semi(ref second) = w[1].node,
332 let ExprKind::Assign(_, ref call) = second.node,
333 let ExprKind::Call(ref closure, _) = call.node,
334 let ExprKind::Path(_, ref path) = closure.node
336 if sp_ident.node == (&path.segments[0]).identifier {
337 span_lint(cx, REDUNDANT_CLOSURE_CALL, second.span, "Closure called just once immediately after it was declared");